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Full text of "Alaskan glacier studies of the National Geographic Society in the Yakutat Bay, Prince William Sound and lower Copper River regions"

254
ALASKAN GLACIER STUDIES
ence to Port Valdez Fiord, testify to differential ice erosion. The heights at which the valleys hang are roughly proportional to the size of the glaciers which occupied them and to the power of the glaciers whose erosion left them hanging.
Just after becoming detached from the Port Valdez Glacier, Shoup Glacier seems to have halted at the mouth of its bay, and to have spread out in a small piedmont bulb long enough to build a submarine deposit at the lip of its hanging valley; for here the
FIG. 26.   SUBMARINE) CONTOUBB OF POET VALDHZ.
After U. S. Coast and Geodetic Survey.    Soundings in fathoms.    Contour interval 100 feet. Banging valleys shown by the letter h.
water now decreases in depth from forty-five fathoms within the bay to one or two fathoms just outside of it. This shoal at the bay mouth, and the sandspit upon it could hardly have been built in water 45 to 68 fathoms deep had not a morainic foundation been provided; and it is noteworthy that the deposit is just so located, and of just such shape, as a bulb glacier would build up here. After this period of halting Shoup Glacier seems to have retreated fairly steadily.
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Fict. 27.   NATURAL SCALE CBOSS-SBCTION or POHT VALDHZ.
GLACIATION OF VALDEZ FIOED
It is evident that the entire Valdez Fiord has been at a former period deeply filled with a great glacier, tributary to the Prince William Sound glacier. We made no determinations of the exact height to which this glacier extended, but Grant and Higgins1 estimate the height reached on the south side of Port Valdez as about 3200 feet.
As already stated, there are several visible hanging valleys on either side of the Port
i Giant. U. S. and Higgins, D. P., Bull. 443, U. S. Geol. Survey, 1910, p. 19.